Avalanche Forecast
Issued: Feb 4th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
shorton,
Avalanche Canada
Snowfall amounts have varied across the region. Triggering slab avalanches is likely on slopes that have been loaded by new snow and wind.
Summary
Confidence
Moderate - Forecast snowfall amounts are uncertain.
Weather Forecast
TUESDAY NIGHT: Another frontal system passes through the region with 10-15 cm of snow, moderate to strong wind from the west and freezing level climbing to 1000 m.
WEDNESDAY NIGHT: Easing flurries as the front leaves the region mid-morning and another 5 cm of snow throughout the day, strong wind from the west, freezing level drops to valley bottom with alpine temperatures around -4 C.
THURSDAY: Mainly cloudy, light wind from the west, alpine high temperatures around -7 C.
FRIDAY: Mix of sun and cloud, light wind, alpine high temperatures around -10 C.
Avalanche Summary
Reports continue to come in of large (size 2-3) natural storm slab avalanches that ran during the storm late last week and into the weekend. Notably, the movement of a large snow machine on Saturday managed to remote trigger a very large (size 3.5) slab avalanche in the Kispiox area. This avalanche failed on the deeply buried surface hoar layer from early January, with a crown fracture of 50-200 cm deep.
Snowpack Summary
A second frontal system will bring another 10-15 cm of snow on Tuesday night. This will bring two day storm totals anywhere from 15-35 cm across the region. With these amounts the most dangerous storm slabs will be on wind loaded slopes.
A weak layer of facets that developed during the mid-January cold snap is now buried 50-100 cm below the surface. Below treeline this layer rests on a melt-freeze crust and a well settled snowpack.
In most areas of the region, the early January surface hoar layer, now buried 150-200 cm deep, is considered dormant. It remains a more active concern in the Kispiox area and further north. Recent activity on this layer, although isolated, is noted in our avalanche summary.
A deep crust/facet layer lurks at the base of the snowpack, especially in shallower (eastern) areas that was reactive earlier in January. While it is promising that last week's snowfall did not trigger avalanches on this layer, there is some uncertainty about the possibility for avalanches in surface layers to step down to it. Triggering this layer is most likely in shallow, rocky start zones or with a large load such as cornice failure or avalanche.
Terrain and Travel
- Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
Problems
Storm Slabs
Variable amounts of new snow will build new surface instabilities on Wednesday. In the west of the region, heavier snowfall will result in thicker storm slabs while closer to Smithers lighter snowfall combined with elevated southwest winds will form touchy but less widespread wind slabs.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
Isolated very large persistent slab avalanches during recent storm cycles have shown rapid loading can produce very large and destructive avalanches that fail much deeper than our storm snow depth. With another strong storm passing through the region, similar isolated persistent slab activity may occur. Particularly concerning areas include Kispiox and further north, as well as the west of the region.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Feb 5th, 2020 4:00PM
